1. Field of the Invention
This invention relates to improvements in methods for assembling machines. More particularly, it relates to a method for assembling the parts of a waste materials filtering apparatus in a way that substantially prevents misalignment and jamming of the apparatus.
2. Description of the Prior Art
U.S. Pat. No. 4,597,864 to Wiesemann discloses an apparatus for continuously removing relatively large items of waste materials from a water stream as a preliminary treatment of water at a municipal or industrial water or wastewater treatment facility. The apparatus sits in a channel within which flows a stream of water containing solid waste. It includes a rotating screen assembly having parts designed to lift solid matter from the stream of water as said stream flows through the apparatus.
The rotating screen assembly includes a plurality of vertically disposed, laterally spaced apart rotating screen segments that collectively form the screen, with the lateral spacing between contiguous rotating screen segments limiting the size of the waste materials that can flow past the machine and into downstream treatment stations where smaller particles are removed from the water. Each rotating screen segment is formed by a plurality of link members that are disposed in articulated relation to one another and which collectively form a loop of link members which revolve in a vertical plane. The trailing end of each link has an integral horizontally-extending part that lifts solid matter from the stream as the screen segments travel upwardly on the upstream side of the machine. Means are provided at the discharge end of the apparatus for dumping the matter so lifted into a solid waste collection container.
The screen assembly is rotated by a plurality of laterally spaced apart motor-driven sprocket segments positioned generally at the discharge end of the apparatus. The sprocket segments are positioned in offset relation to the individual links so that as the links pass thereover, the sprocket segments enter into the spaces between the links.
The apparatus performs its intended function, but it is subject to jamming because the apparatus performs well only when the sprocket segments are perfectly or almost perfectly aligned with respect to each contiguous set of links. Due to the large number of links, the alignment is not easily maintained. Even when the sprocket segments and links are in their respective ideal relative positions, the sprocket segments rub against their contiguous links in alternating succession, displacing each link about one-sixteenth of an inch per rub. More particularly, the links are displaced in a first direction in a first rub, and are displaced in an opposite direction during a second rub. Due to the rubbing and alternating displacement of the links, the sprocket segments and links eventually become misaligned and collide with one another. This bends the links, damages the sprocket segments, and prevents further rotation of the rotating screens until the apparatus has been disassembled and new links and sprocket segments installed. The repair procedure typically takes several days, during which time the municipality's water treatment system is incapacitated.
There has been a longstanding need for a new design that would prevent or at least substantially prevent the misalignment problem, but no solution has been apparent to those of ordinary skill the art.